A machine for spinning or twisting yarn as taught in German Patent application 34 41 230 (see also the abovementioned copending applications) can comprise a plurality of operating units such as spindle whorls (that is, operating elements which rotate at high speed). Groups of these operating units are each drivable by a respective endless tangential drive belt coupled to a drive having a motor. Additionally overlappingly located tangential drive belts generally run around two guide rollers at each end of the respective belt.
By "operating unit" I mean here a machine element with a high rotational speed, for example, a spindle in a spinning or twisting machine or a rotor or a disentangling roller in an open ended spinning machine.
When a tangential drive belt breaks in such machines, under certain circumstances the rupture is not immediately noticed, since the other tangential drive belts generally keep running unchanged. This is particularly true when the belt that breaks is located in the middle of the length of the machine. This kind of belt breaking, for example, in a ring spinning machine, leads immediately to a plurality of yarn breakages, which can overload the yarn suction removal system of the machine. The yarn pieces can no longer be drawn away and wind and tangle on the rollers, which can lead to severe damage to the machine.